I would use what you already have. Why would you buy a different set of pistons for a little bit more compresson? Then you are going to have to get new pistons pressed onto the rods. You might not even notice the difference in the performance. You can buy a used roller cam on Ebay, they are reuseable. If you don't want what you already have sell it. It might not be easy to sell and then you will have to find something else.